Belgium bombings raise security worries at U.S. airports
| Reuters

NEW YORK Major U.S. airports were on high alert on Tuesday, with police out in force after at least 30 people were killed in suicide bombing attacks on Brussels airport and subway, though officials said there was no specific threat to the United States.

U.S. President Barack Obama and Democratic presidential election contender Hillary Clinton vowed to do more to take on militants, while Republican presidential front-runner Donald Trump called for tighter border security and suggested U.S. intelligence services could use torture to head off future attacks.

The Obama administration was expected to tighten security at U.S. airports following the Brussels airport attack, which occurred in a public hall outside of the security check area.

U.S. Representative William Keating of Massachusetts, the ranking Democrat on a House subcommittee on terrorism, said the Brussels attacks illustrate the difficulty of protecting "soft targets" outside tightly controlled security cordons.

"We should learn from this that the targets aren't going to be just getting on the plane itself, but the airport in general," Keating said in a phone interview.

U.S. Homeland Security Secretary Jeh Johnson said the agency has no intelligence that would point to a similar attack being plotted against the United States.

Islamic State, a militant group that has gained control of large areas of Iraq and Syria and has sympathizers and supporters around the world, claimed responsibility.

Delta Air Lines Inc (DAL.N), United Continental Holdings Inc (UAL.N) and American Airlines Group Inc (AAL.O) cancelled or rerouted flights as a result of the attack.

Large numbers of uniformed police officers and National Guard members in fatigues and carrying long weapons patrolled New York's John F. Kennedy International Airport.

One guard member was overheard telling a colleague "we have to keep an eye out for bags" after reports that many of the wounded at the Brussels airport had severe leg injuries, a pattern that suggests an explosion at ground level.

The U.S. State Department said on Tuesday that an undetermined number of U.S. citizens had been injured in the Brussels attack but that none had been killed. Three Mormon missionaries and a U.S. Air Force member and his family were among the Americans hurt.

'SCOURGE OF TERRORISM'

Obama addressed the attacks briefly in a speech in Havana on his historic first visit to Cuba, vowing to support Belgium as it seeks out those responsible.

"This is yet another reminder that the world must unite. We must be together regardless of nationality or race or faith in fighting against the scourge of terrorism," Obama said.

Islamic State was blamed for killing 130 people in Paris last November. Then in December, a married couple inspired by Islamic State shot dead 14 people in San Bernardino, California.

The attacks in Belgium drew immediate response from candidates seeking their party's nomination to run for the White House in the Nov. 8 election.

Former U.S. Secretary of State Clinton vowed to strengthen her drive to "defeat terrorism and radical jihadism."

Billionaire Trump told NBC's "Today" program: "If they could expand the laws, I would do a lot more than waterboarding. You have to get the information from these people."

He was referring to the practice of pouring water over someone's face to simulate drowning. Obama banned its use by U.S. interrogators.

The attack raised worries among some U.S. Muslims that they could face more hostility in the wake of an attack by Islamist militants, though mainstream Muslims have repeatedly denounced violence.

"The media hype and political manipulation heightens our concerns," said Sheikh Shaker Elsayed, imam of the Dar Al-Hijrah mosque in Virginia.

While the attack immediately sparked discussion of further strengthening U.S. airport security, some pointed out the inherent difficulty of securing spaces that offer broad public access.

"There are limits to exactly how exhaustive those perimeters can become," U.S. Secretary of State John Kerry said in an interview with Telemundo. "So people need to be vigilant, everybody needs to take precautions."

Some travellers expressed concern that new security measures at airports, which have already imposed extensive restrictions since the Sept. 11, 2001 attacks on New York and Washington, would cause more inconvenience without improving safety.

"It already takes all day," said Hans Vermulst, a 66-year-old construction materials company owner who was at New York's Kennedy airport trying to get home to Holland after his connecting flight to Brussels was cancelled. "We have to take it as it comes, but I'm not happy with it."